On the various modes of flight in relation to aeronautics / by James Bell Pettigrew.

Date:
[1867]
Catalogue details

Licence: Public Domain Mark

Credit: On the various modes of flight in relation to aeronautics / by James Bell Pettigrew. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    For this reason flight is the most laborious, and in some respects the most complicated and difficult, of all the animal movements. The peculiarities of the different media, as far as locomotion is concerned, may be briefly stated. On the land we have the maximum of resistance and the minirrmni of displaceme nt. In the air, the minimum of resistance and the maximum of dis- placement. The water is intermediate in these respects. As a consequence, the feet of land animals are small—their bodies large. The horse and deer furnish examples. In those land animals which take to the water occasienally, or the reverse, the feet are enlarged and usually provided with a membraneous expansion between the toes. Of such, the otter, omythorynchus, se^, frog, tm'tle, and crocodile may be cited. In addition to the land animals which run and swim, there are some which precipitate themselves, parachute fashion, from immense heights, and others which even fly. In these the membraneous expan- sions are greatly increased—the ribs affording the necessary degree of support in the dragon or flying lizard, the anterior and posterior extremities in the flying lemur, flying cat, and bat. Although no lizard is at present known to fly, there can be little doubt that the extinct pteredactyles, which are intermediate between the lizards and crocodiles, were possessed of this power* The bat is interesting as being the only mammal at present enjoy- ing the privilege of flight; it is likewise instructive as showing that flight may be attained without the aid of hollow bones and air-sacs, by purely muscular efforts and by the mere contraction and dilatation of a continuous membrane. If we now direct our attention to the water we find that the amount of surface engaged in locomotion greatly exceeds that in the amphibia. The fish furnishes the best example. In it the lower haK of the body and the broadly-expanded tail are applied to the water very much as an oar is in sculling. The sea-mam- mals, as the whale, dugong, manatee, and porpoise, swim in precisely the same manner as the fish, with this difference that the tail strikes from above downwards, or vertically instead of horizontally, or from side to side. The seal is exceptional in this respect. The animals which furnish the connecting link between the water and the air are the flying fishes on the one hand, and the diving birds on the other: the former sustaining themselves for considerable inter- vals in the air by means of their enormous pectoral fins, the latter using their wings for flying above and beneath the water, as occasion demands. I have carefully examined the relations, structure, and action of the fins in the flying-fish, and am of opinion that they act as true pinions; their inadequate dimonsiens only preventing them from sustaining the fish for an indefinite period in the air, at all events so long as they
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